hughes



2 Sheets -Sheet 1.

J. HIUGHIEJS= FURNACE FOR BURNING PYRITES FOR THE MANUFACTURE OFSULFURIC ACID AND OTHER PURPOSES.

N0. 65,914. Patented June 18; 1867.

2 Sheets-Sheet 2. J HUGHES. FURNACE FOR BURNING PYRITES FOR THEMANUFACTURE OF SULPURIC ACID AND OTHER PURPOSES.

No. 65.914. Patented June 18, 1867.

Quint tatts @strnt firs JOHN HUGHES. OF EDGEWATER, 'NEW YORK.

Letter Patent No. 65,914. dated June 18, 1867.

IMPROVED FURNACE FOR BURNING PYRITES FOR THE MANUFACTURE OF SULP HDRIOACID AND FOR OTHER PURPOSES.

dip Srgetulc more in llitSt littus flaunt ant making out at the same.

TO ALL WHOM IT'MAY CONCERN:

Be it known that I, JOHN HUGHES, of Edges-titer, in the county ofRichmond, and State of New York,

have invented a ncw and useful Improvement in Furnnesfor Burning PyritesWithout the Aid of Fuel; and I do hereby declare that the following is afull, clear, andexaet description thereof, which'will enable othersskilled in the art to make and use the same, reference being bad to theaccompanyingdrawings, forming part of this specification, in whichiFigure 1, Sheet 1, is a vertical section of a block of furnaces of myimproved plan 'of construction taken in the line 2: :c, fig. 3, sheet 2.

Figure 2, a horizontal section of the same taken in the line yy. Figure3, Sheet 2, a front vi'ew of 'a block of my improved furnaces, with'theouter wall removed fromone furnace, showing its interior in verticalsection.

Figure 4, a detached view of the door-plates of a single furnace.-Similar letters of reference indicate like parts. i My invention relatesto anew and improved plan of construction of furnaces or kilns forb'urningiron or other pyritcs to expel the sulphur, either for thepurpose of utilizing it in the manufacture of sulphuric acid or forextracting the metals which may be associated with the mineral.

The pyrites are burnt in my improved furnace without the aid of fuel tomaintain combustion, after the tire has been started with coke or othersuitable kindling stuff, by the ignition of the sulphur alone. Thepyrites are fed in at the top, and the desulphurizod mineral iswithdrawn from the bottom.

Furnaces for burning iron pyrites without the aid of fuel are not novel,but their plan of construction difi'ers materially from that of myinvention, and they differ essentially in the results of theiroperation. The nearest in their plan of construction to my improvedfurnace are those employed at. various chemical works at St. Helens,Wiggin, Manchester, and other places in Great Britain, for themanufacture of sulphuric acid.

These perpetual-burning furnaces are described by Professor Muspratt, inhis Chemistry as applied and relating to the Arts and Manufactures, page1024, volume 2, from which are made the following extracts:

The structure of a pyrites kiln is shown in Figures 576, 577.

In Figure 577 the pyrit'es is shown as enclosed on two sides by twosloping walls, the back and front walls being vertical.

The mass of pyrites rests on iron bars in the same manner as an ordinarycoal fire; the air rushes upfrom what, in an ordinary furnace, would bethe ash-pit, and wends its way through the crevices and interstices ofthe mass tofeed the combustion.

Sometimes the combustion goes on at a rate so rapid that the pyri'tcsbecome fritted or enter into a semifused state. Sometimes the whole massgets fused together, In such acase the brick closure is removed for thepurpose of introducing a crow-bar, or other such instrument, in order tobreak up the mass or break a passage through.

Much care and attention are required to burn pyrites well. It is nouncommonsthing to find, on examining the waste heap of a manufacturer,that a great quantity has been removed little more than half burned.

It will be observed by these statements of Professor Muspratt, that theplan of construction of these furnaces employed in England for burningpyrites is quadrangular, the sides sloping from topto bottom, and theback and front being vertical; and also that the operation is veryimperfect in d-esulphurizing the mineral at all times, while theyareliable to interruption from fusion or slugging.

I have been for many years engaged in the manufacture of sulphuric acidin England, with furnaces similar in construction to those described byProfessor Muspratt, which are in use there to this'day, and in myexperience thesame difliculties have always attended their'working. Theresiduum or waste is always so highly charged with sulphur remaining init as to be very noxious when withdrawn from the kilns, requiring theworkmen to cover their nostrils with wet cloths to protect them fromtheelfcts of the sulphurous gases; and analysis constantly shows over sixper centoof sulphur remaining. The mineral often slugs or fuses into asolid mass when the crow-bar fails to break it up, and the only remedythen is to break out the front of the kiln and remove it bodily, whichoften brings away the fire brick lining with'it. This happens at leastonce a week, and frequently twice a week, with each set of kilns.

The operation of removing the moltcninass is very laborious anddisagreeable, and the repairs of the kilns expensive. It is alsodifiicult to get men to do this work. These difiiculties 'in the workingof the pyrites burning kilns described arise from a faulty plan ofconstruction, both as to form and proportion, which has been corrcctedinmy improved kilns. They are too large, and carry so heavy a burden ofmineral, that the heat becomes excessive and renders them liable to slagit, while the bearing of the mass of mineral is so unequal at the sidesand corners that it crushes down without check from the top to thebottom, rendering the withdrawal of the burnt part of the materialdifficult, and quite impossible without an admixture of unburnt pyrites.

Myimproved kiln or furnace is builtround or oval, instead ofquadrangular, and tapers regularly from top to bottom, except on thefront side, which has a flat, vertical face for the doors,'ashereinafter described. This difference in the plan of construction,between my improved furnace and thequadrangular furnace in use, 'isvery-important practically. "The curved taper sides bind, nnd canse themineral to bear equally at all points,

the pressure tending to the centre, on the principle of an arch, and themineral supports itself, instead of crushing down, as in thequadrangular furnace, so that it settles gradually as the sulphur burnsout; and when the residuum is withdrawn all'above stands undisturbeduntil the mass is broken down to fill the space of that portion takenaway at the bottom. In the quadrangular furnace the heat is not equallydistributed throughout all parts, the centre being at a much. highertemperature than the corners, where, consequently, the mineral does notbecome thoroughly desulphurized unless the fire is raised higli enoughto produce fusion in the centre of the mass, which is'the constanttendency of the attempt to burn the mineral thoroughly in the corners.In my improved curved-sided furnace the heat is equally distributed atthe centre and sides, and the mineral is all burnt alike withouLthenecessity of raising the tires high enough to fuse the mineral, andconsequently it is all thoroughly desulphu-rized in its passage downthrough the furnace. This result of the operationof my improved furnacehas been demonstrated conclusively by the working of a trial set erectedat the Richmond Chemical Workson Staten Island, where six kilns were runnight and day, without interruption, for more than three months, andwere only put out of blast recently for reasons aside from theiroperation. The burnt pyrites dis charged from these furnaces were socompletely desulphurized that no odor was perceptible when they werewithdrawn,and-when cold a critical examination failed to detect anyunburnt mineral; indeed the sulphur in the residuum ishardly'appreciable upon chemical analysis.

Another important advantage resulting from my improved plan ofconstruction is, being able to charge with large lumps of mineral,instead of breaking it up into small pieces, as heretofore required,thus saving labor and avoiding fin'edust, which is difficult to burn ina kiln.

The dimensions, as well as the proportions, of a-kiln for burningpyritcs successfully arevery important. If made too large in capacitythe body of ore is likely to produce too powerful a combustion and fusethemass, and if too small it is difficult to maintain combustion at all.I have avoided these extremes.

The kilns may be built singly or in blocks of any desired number, inpairs placed back-whack; but for the manufacture of sulphuric acid'Iprefer a block of six kilns, which will be herein described. For makingsulphuric acid, arched crowns and fines, leading the sulphurous vaporsto condensing-chambers, are necessary; but. for: desulphurizing metallicpyritous ores the kilns may be built with open tops, like lime-kilns, todischarge into the open air; but a stack, with flues leading to it, isalways preferabl to get rid of the gas.

A represents a block of six kilns, B B, arranged in pairs, with frontson opposite sides. 0 is a stack connected with a condensing-chamber; E,a main flue, and D D branch flues leading from the kilns into it. The

main fine E runs across the block A, and is provided with doors a a atthe ends, for the introduction ofpots d dcontaining nitre and sulphuricacid for making sulphuric acid. A flue or open passage, K, runs throughthe bottom of the block, between the kilns, to equalize the temperature.The block of.kilns is built of brick, about eleven feet square and eightfeet six inches high, and is strongly bound at the corners with heavyangle-iron, and with rods running across the sides at top, middle, andbottom. The kilns are made in theform of inverted truncated cones,tapering from the. top to the bottom of the block, in the proportion ofabout two and a half feet diameter at the top of. the kiln and one footat the bottom. The front side of the kilns is faced or flattenedvertically for receiving doors. Heavy cast-iron door-plates F F arefitted in the front. They are about two feet wide and six feet threeinches high. Four flanged door-openings b b are made in the plates, theflanges cast on them andprojecting eight inches into the brick-work,with their back open ends flush with the face of'the kiln. The furnacesor kilns are made without grete-bars. The bottomis level with the lowerside of the lowest dooropeuing. On the iron platesFF are groovedprojections c c for holding the sliding-doors G G, which set in pairsover each of the openings 6 meeting centrally when closed. Small holesare made in the upper doors for observing the fires. The holes may becovered with mica or luted with clay, as are the crevices of the doorswhen the furnace is in operation.

The ma n'agement is very simple-and easy. The fire is started with coke,or other suitable kindling stud, and after the kiln has become highlyheated the pyrites are introduced at the top of the kiln, by light andgradual charges, until the combustion is regular and well established.The draught is regulated by opening the lower doors more or less, asrequired; and when the blue flames of the sulphur die out at the top ofthe charge the burnt mineral is withdrawnfrom thebottom. This is donewithout disturbing the mass of the urineral above, which is held incheck by its equal, arch-like bearing towards the centre from the sides;and after the-withdrawal of the desulphurized mineral the doors nextabove are opened, and a sufficient quantity of the mineral is brokendown with a crow-bar, to fill the empty space below, as required. Acharge of fresh pyritcs is added occasionally, and the operation iscarried'on with closed'and luted doors, except those tit the bottom,

which sup 1 .the'necessary draught. Tlius my improved'pyrites-burningfurnaces may be kept continuously in operation, without the aid of fuel,with great economy and efiiciency, either for the purpose of utilizingthe sulphurous vapors or extracting the metals, especially gold andsilver, from the thoroughly desulphm-ized mineral.

Having thus described my invention, I claim as new, and desire to secureby Letters Patent- Constructing a furnace for burning pyrites or.sulphurets of iron, copper, zinc, or other metals, without the aid offuel, in the form of en inverted truncated cone, without grate-bars, andprovided with doors on the front side, ranged one above another from topto bottom, substantially as and for the purposes herein described.

JOHN HUGHES.

Witnesses:

WM. F. McNAMAnA, ALEX. F. Ronnnrs.

